V00.76 opt-in module: Nimbus JOSE+JWT-backed default implementation of the jCustos-core JWT SPIs (JwtValidator, JwksClient, JwtValidatorFactory) plus the JwtDiagnosticContributor. Framework-neutral — no Vaadin, no REST framework. The JOSE-free SPI contracts and result types live in jCustos-core/jwt/api; this module is the only place a JOSE library is on the classpath.